旋翼涡环状态气动特性和参数变化的风洞试验

为了研究旋翼下降和涡环状态的流场及气动特性,在中国空气动力研究与发展中心Φ5m立式风洞中,完成了BO-105直升机桨尖马赫数相似旋翼模型的流场和测力试验。试验获得了旋翼悬停和垂直下降状态桨盘附近的流场,同时测量得到了模型旋翼拉力、扭矩等参数的变化。试验结果表明:高速粒子图像测速法(PIV)相机成功捕捉到了下降率增大时旋翼涡量向桨盘附近聚集的过程。垂直下降率在0.9左右时旋翼拉力和扭矩最小,分别只有对应总距角悬停状态拉力的60%和80%左右。在深度涡环状态,旋翼周围存在大尺度涡结构周期性形成和破碎现象,这种现象是旋翼拉力和扭矩剧烈波动的原因。斜下降相对垂直下降而言,旋翼的拉力和扭矩损失都较小。抛物线桨尖外形与常规的矩形桨尖外形相比,垂直下降气动特性并无显著区别。 

Wind tunnel test of aerodynamic characteristics and parametric variation for rotor in vortex ring state

In order to investigate the flowfield and aerodynamic characteristics of rotor in descent and vortex ring state, a BO-105 model rotor with tip Mach number similarity was tested in Φ5m vertical wind tunnel of China Aerodynamics Research and Development Center. Flowfields around blade tip in hover and descent flight were captured, and variations of rotor thrust and torque were obtained. The process of vorticity accumulation with the increase of rotor descent rate was observed through application of high speed PIV(particle image velocimetry) camera. When vertical descent rate was 0.9, rotor thrust and torque were at the lowestlevel, and the value was only 60% and 80%, respectively, of that in hovering state. The formation and break down of large scale vortex structure were observed in deep vortex ring state. Violent fluctuation of rotor thrust and torque in vortex ring state was caused by this phenomenon. Oblique descent had less thrust and torque loss than vertical descent. Aerodynamic characteristics of parabolic blade tip were similar with those of conventional rectangular blade tip in vertical descent.